1. Field of the Invention
The present invention relates to a method for producing a boron nitride film, in particular, a cubic boron nitride film, which can be applied to a cemented carbide tool, an insulating film, a heat transfer film, a semiconductor, etc.
2. Description of the Related Art
For producing cubic boron nitride (hereinafter sometimes referred to as "c-BN"), following three methods are known:
1. A method comprising depositing boron on a substrate from a vapor source containing boron and simultaneously irradiating ion species containing at least nitrogen onto the substrate from a source for generating said species to produce a cubic boron nitride film on the substrate (see Japanese Patent Kokai Publication No. 181262/1985).
2. A method comprising chemically transporting boron by H.sub.2 +N.sub.2 plasma to produce cubic boron nitride on a substrate (see J. Mat. Sci. Let., 4 (1985) 51-54).
3. A method comprising evaporating boron with a hollow cathode discharge gun (HCD gun) while ionizing nitrogen with a hollow electrode and irradiating ionized nitrogen onto a substrate on which radio frequency wave is applied to produce boron nitride on the substrate (see Inagawa et al, Proceedings of 9th Symposium on Ion Source Assisted Technology, '85, Tokyo, 299-302 (1985)).
However, it is difficult to produce cubic boron nitride having good crystallinity by the above conventional methods. That is, by the conventional methods, a single phase film consisting of c-BN is not produced, and the c-BN film contains hexagonal system boron nitride (hereinafter sometimes referred to as "h-BN") and/or amorphous boron nitride.